Question: If $(x,y)$ is a solution to the system
\begin{align*}
xy &= 6, \\
x^2 y + xy^2 + x + y &= 63,
\end{align*}find $x^2 + y^2.$
Solution: The second equation factors as $(xy + 1)(x + y) = 63,$ so $7(x + y) = 63,$ or $x + y = 9.$  Then
\[x^2 + y^2 = (x + y)^2 - 2xy = 9^2 - 2 \cdot 6 = \boxed{69}.\]